PROJECT REPORT
ON
DELHI METRO – COMPARISON OF TECHNIQUES
AND METHODS FOR CONSTRUCTING ELEVATED
CORRIDOR AND ITS ENVIRONMENTAL EFFECT
(Prepared under guidance of Shri N. LALWANI, Sr. Prof. Bridge-2)
BY-
D. S. MEENA
CHIEF GENERAL ENGINEER
N. W. RAILWAY
(REFRES HER COURS E- NO. 9208)
INDEX
1.
INTRODUCTION.
2.
GENERAL CRETIREN FOR SELECTION.
3.
SPECIAL REQUIREMENT OF ELEVATED
CORRIDO T.
4.
CONSTRUCTION METHODOLOGY.
5.
EREC TION OF SEGMENTS
6.
AIRPORT LINE.
7.
METHOD STATEMENT.
8.
PER KM COST.
9.
QUALITY CONTRO LL.
10.
ENVIRONMENTAL IMPACTS
11.
CONCLUSION
DELHI METRO - COMPARISON OF VARIOUS
TECHNIQUES AND METHODS FOR CONSTRUCTING
ELEVATED CORRIDOR AND ITS ENVIRONLMENTAL
IMPACT ASSESSMENT
D. S. Meena
Chief General Engineer,
N. W. Railway,
Jaipur, Rajasthan-302006
1.0 INTRODUCTIO N
With a view to reducing the problems of Delhi commuters like congestion
on roads, ever slowing speed, increasing accidents rate, fuel wastage, and
environmental pollution, Delhi Metro Rail Corporation Lim ited has under
taken the construction of Mass Rapid Transit System for Delhi. The entire
work of length approximately 413.83 km, planned so far is divided into four
partsPhase I
65.10 km
Phase II 128.06 km (110.98 km in Delhi + 17.07 in Non Capital Region)
Phase III 112.17 km ( 62.30 km in Delhi + 49.87 in Non Capital Region)
Phase IV 108.50 Km ( 97.00 km in Delhi + 11.50 in Non Capital Region)
The phase I and Phase II of the system consists of 193.16 km route length
out of which a major portion, i.e. 142.31 km (125.23 km in Delhi and 17.08
km in NCR) of the system is supported on the viaducts, 6.5km at Grade and
44.35 under Ground.
The construction of the superstructure of such long distance of viaducts has
not only to meet the functional requirement but also to take care of the site
constraints such as
i)
Allowing free flow of vehicular traffic on the already congested
along with chosen alignment,
ii)
Paucity availability of land,
iii) Existence of charted and uncharted utilities,
iv)
Problems to pedestrians,
v)
Problems to existing residents, and
vi)
Environmental impact including noise and vibration etc.
Present project report describes the comparison of various technique and
methods adopted in construction of the viaduct and examines together the
various factors influencing the design.
The design solutions are
presented together with methods adopted to comply with very tight
design and construction period.
2.0 GENERAL
To select the type of Metro Rail corridor I. A comprehensive multimode mobility study, taking into account the
various transport means like Rail/Sub urban / Metro/Roads/Feeder
services, is required to be conducted to finalized the change over
points.
II. A combination of route i.e. elevated, at par, and under ground is then
selected considering their –
•
•
•
•
•
Construction cost
Maintenance cost
Aesthetical view
Environmental impact, and
Impact on the profile of the city
The elevated corridor is planned by DMRC generally to cut across fairly
densely built up areas by virtue of its need to serve these area “Hence its
impact needed sensitive treatment and assessment. Thus, the sometimes
conflicting issues of operations and using requirements, construction
appearance, environmental impact, including noise and vibration had to be
included in the overall assessment of the most appropriate materials and
form of construction.
3.0 SPECIAL REQUIREMENTS OF ELEVATED CORRIDOR
3.1 DURI NG CONS TRUCTIO N
As stated in Para 1.0 above construction of the superstructure of such long
distance of viaducts has not only to meet the functional requirement but also
to take care of theSite constraints such as Allowing free flow of vehicular traffic on the already congested along
with chosen alignment,
Paucity availability of land,
Existence of charted and uncharted utilities,
Problems to pedestrians,
Problems to existing residents, and
Environmental impact including noise and vibration etc.
Mitigation MeasuresTo have minimum inconvenience to general public the following m itigation
measures are required
• Fully barricading the construction corridor,
• Providing proper signage and lighting arrangement,
• Completing the construction in a minimum time frame and in a time
bound manner,
• Good house keeping of the surrounding area, and
• Rais ing the confidence of the public by adopting safety measures,
caring for public attitude
4.0
CONSTRUCTION METHODOLO GY
4.1 Structure Form Adopted
The structural form adopted for the elevated Corridor (i.e. viaduct)
constructed so far by the DMRC is comprises of
Pile foundation - Group of bored piles of dia 1.0 m , 1.2m, and
1.5m.
Required concrete pile cap, pier and cross heads( cast in situ/pre
cast pier heads )
Pre cast Pre stressed concrete segments of type• single segmental U,
• single segmental box,
•
•
•
•
segmental box,
segmental U,
Full U girder one for each track
Pre cast pre stress I girders
cast in situ span, and
Special span
4.2 SINGLE S EGMENT CONS TRUCTIO N
4.2.1 Constructivity Requirement for single segmental girders
• Transportation of long girders having spans more than 20m by
trailor will pose serious problem in crowded city roads and sharp
curves.
• Operation of Two cranes to place girders in position will require
traffic block during night for a number of night which may not be
acceptable to traffic police and if agreed upon they will cause
inconvenience to general public.
• The availability of casting yard at suitable location as choice will
be governed by shifting, lifting and transportation of girders.
• Cast in situ construction, Where ever required, is time consuming
and cause inconvenience to public.
4.2.2 Advantage of single girder for two track s over two girder
Single girder for two tracks have got following advantage over two
girdersi) 4m pier cap against 6 to 7 m for two girder
ii) 50% bearing
iii) Gives a clean soffit and is preferable authentically
4.2.3 Disadvantages of single girder
i)
Larger spans have to be cast-in-situ which will cause false
work, shuttering and concreting problem
ii)
It can not have curved surface in play
iii)
It is not idle suitable for carrying spans which are
unavoidable in city due to road crossings, utilities and
other constraints.
4.3
WHY S EGMENTAL CONS TRUCTIO N IS PREFERED?
The various reasons arei)
If a decision is taken to go for single girder for two tracks
then segmental casting is only option. It can be managed
from 3 to 4 casting yards for one full leg of corridor
located at available land which may be a few km away.
ii)
Very fast Progress can e achieved.
iv)
Segments can be cast and stacked parallel to pile and pier
construction activity.
v)
Launching speed is very fast.
vi)
Cause minimum disturbance to traffic as segments can be
fed at selected location and launched with help of
launched spans moving it on completed deck to avoid
lifting of segment from trailor positioned on road.
vii) It can have curved surface in plan and is suitable for
carrying span lengths.
viii) In case some span have to be skipped due to local
problems segmental casting has got flexibility.
ix)
Cost of construction may be slightly more to start with but
if it is adopted on large scale it may come down and likely
to be comparable with conventional construction.
5. ERECTION OF VIODUCT
The superstructure is be erected entirely from below using an under slung
erection tackle.
Three type of erection tackle are used
1. BRIDGE CONEDesign by Bombay based firm, moves pier to pier no ground
support is required.
2. SPIC
Design by Italy based Firm .Nois ing girder is supported on
ground, can not be used where R. L. as road vehicle can not be
moved. Much Safer and very use full for Railway x-ings.
.
3. KHANOLKER
Design by Bombay based firm, front leg is moved ground, can
not be used where x- ing is required.
6. AIRPORT LINK
6.1
Different type of structure has been adopted due to special nature
of requirement of airport link.
i) Two types of super structure was adopted.
a) 25m long span U girder.
b) Continuous span PSC solid slab at special. Locations
i.e. Dhoulakuan fly over.
ii) Pre cast Pier Cap
iii) Other structure All foundation and other substructure works are
cast in situ. This includes-foundation pile and pile cap
- Piers
-Abutments
-Extended pier arm
- Cantilever pier arms and portal piers
6.2 Bearing
-Elastomeric bear ing are placed underneath U- girder for transfer
of vertical forces
-Concrete shear keys are provided at top of pier cap which restrain
the movement of deck in transverse direction and acts as topper in
longitudinal direction.
A gap of 25mm between deck and shear key each side of the deck
is maintained to allow thermal expansion of the deck.
6.3 Drainage of deck/ solid pier
Drain pipe is located with in solid pier to avoid aesthetics
problems.
The top of deck soffit slab is profiled so as to collect run off water
at middle of slab by providing a cross slop of 1%. Two no of
drainage pipes at each end of U girder span have been provided on
top of the pier cap which will connect to the drainage pipe in pier.
6.4 SINGLE U-GIRDER
First time in Delhi Metro
Advantages as compared to segmental box section
– Cost effective as the weight 11t/m where as it is 16t/m in
segmental box, overall savings is about 10% .
– Fast un erection it takes less than one day cycle in erection of
one span compared to 5-6 days required of conventional
segmental span.
– Aesthetically better looking as no joints.
– No site parapets required.
6.5
SINGLE SEGMENTAL GIRDER
Single segment for two tracks have got following advantage
over two separate grinders :
- 4m pier cap head against 6 to 7m for the box girder.
- 50% bearing.
- Gives a clean soffit & is preferable aesthetically.
- Segmental construction can achieve very fast progress.
Segment can be cast & stacked parallel to pile & pier
construction activity.
- Cost of construction may be s lightly more to start with
but if it is adopted large scale it may come down & is likely
to be comparable with conventional construction.
- In case of some problem, if a few spans have to be
skipped, segmental cast has got flexibility.
11.0 METHOD STATEMENT
A method statement is detailing the procedure of casting
various elements of the structure.
It is to be prepared by the contractor and get it approved by the
client or their nominated consultants well before starting the
construction work at site.
It is a written document, available at site, to be referred by the
client and contractor, as and when required by them, to ensure
availability of required infrastructure and proper sequence of
the construction activities ,so as to get the work done with
desire progress and quality.
7.1
7.2
7.3
7.4
7.5
7.6
Preambles: Casting of proposed U –Shaped girders of 25.0 m
nominal length for Air Port express link of DMRC.
Casting Yard- Located near Airport in Mahipalpur with an area
of 315m X 50 m approx. Constructed as per Drawing No
267/Cy/01. Other details to be mentioned herein are details of
casting beds, no of different moulds, Jigs, Batching Plant,
Rebar Yard, Stacking Area, water tanks ,Excess Road, Office
Block, Laboratory, Over Head Gantry, Sheds to Keep var ious
Tools and Plants etc.
Reference Drawing:- Details of the drawings illustrate the
complete casting and stacking scheme is to be given under this
head.
List of Moulds and Equipments in casting Yard
Mould: Under this head Details of casting beds along with
details of Approved reference Drawing, Sequence of fixing the
various shutters is to be given here.
Time Cycle for CastingSr.No
Description
Time
1 Cleaning of casting beds and oiling 5 hrs.
2 Fixing of outer shutter
10 hrs.
3 Placing of rebar cage
10 hrs
4 Threading of strands
12 hrs
5 Initial pretensioning
6 hrs
6 Final pretensioning of all strand
2 hrs
Remark
Day
Day 1
Day 1
Day 2
Day 2
Day 2
7
together
Placing of inner mould and
8 Inspection by client
9 Pouring of concrete
10 Curing
11 Removal of inner shutters *
12 Transfer of pre- stress
13 Cutting of strands
14 Lifting of girder
15 hrs
2 hrs
10 hrs
72 hrs
4 hrs
2 hrs
2 hrs
10 hrs
Day 3
Day 3
Day 4
Day 4 – 6
Dar 4
Day 7
Day 7
Day 7
* Inner shutters must be available for casting of 2nd long line on
day 5th so that casting is possible on day 6th
7.7
Rebar cage- No of Jigs required to achieve the planned progress
per week and frequency of checking the condition of jigs as
mutually agreed to be mentioned here.
7.8 Rebar cage – method of cutting and bending of re-bars, their
checking procedure and shifting to casting bed is to be given
here.
7.9 Cover block- Procedure of their casting, required shape (semi
circular) is to be given here.
7.10 Concreting- The sequences of concreting to be mentioned here
for example- Soffit - Web1 - Web2 then top flange on both
sides
7.11 Fixture in girder – here the details of all
the fixture to be
provided are to be given.
7.12 Curing of the Girder- method and time period of curing ,
alternate method etc.
7.13 shuttering- Method and time of shuttering, their placement and
cleaning etc to be mentioned here. Transfer of prestress
7.14 Lifting of girder- Procedure of lifting and placement as per
drawing with required no of pre decided type of cranes to be
given here.
7.15 Inspection before dispatch to the erection site.
Enclosures - For example Risk assessment, inspection test plan
formats etc.
8.0
PER KM COS T
Viaduct
Phase I
Rs. 24 crore/km
Phase II
Rs. 22 crore/Km
Dwarka to Dwarka city Sect. 21
Rs. 19 crore /km (open Foundation)
Tunneling
Rs.110 crore /Km
9.0 Quality Control
9.1
FACTORS FOR SUCCESS
Understand the Client’s Requirements
Identify and manage risks
Team building
Develop good communication and co-ordination
Be one step ahead of the client
Identify problems early
9.2
Establish procedures
DMRC QUALI TU S TRUCTURE
ISO 9001 Standard
Contractors are responsible for QA and QC
Consultants carry out audit roles
Client make decisions
High prior ity given to safety & quality (inspections, audits &
training)
Structured contractor’s record keeping, monitoring, and reporting
9.3
GENERAL AND SPECIAL CONDITIONS
Detailed ISO 9001 Quality Assurance Manual demonstrating the
proposed method to achieve the required quality standards of the
Employer, DMRC
The Engineer shall be entitled to audit any aspect of the system
9.4
Compliance with the quality assurance system does not relieve the
Contractor of any of his duties, obligations or responsibility in the
Contract.
CONTRACT REFERANCE
GCC (General Conditions of Contract)
SCC (Special Conditions of Contract)
Special Specifications
IS and International Standards
Contractor’s Quality Assurance Manual
Contractor’s
Quality
Control
Procedures
(ITPs, Pre-pour and Post Pour Checklists, Sign-offs, As-builts,
Completion Certificates)
9.5
9.1
QUALI TY RES PONSIBILITES
Contractor is responsible for QA & QC
9.2 Contractor submits Quality Plan for approval: 9.3 Method Statement
a) Work Procedures
b) Inspection Test Plans
(Witness, Hold & Document Points)
c) Inspection Checklists
9.4 BASE OF ACCEPANCE CORRIDOR
a) Concrete workability
b) Shrinkage and Swelling
c) Strength
d) Durability
–
–
–
–
9.5
(Water permeability)
Cracking
Cover on reinforcing steel
Aesthetic
REQ UIREMENT
a)
b)
c)
d)
e)
The pour procedure and schedule
Anticipated problems and possible solutions
The formwork design
The concrete mix design
The quality control procedure and the facilities provided by
Contractor.
9.6 FIELD INSPECTION
-Formwork
- Reinforcing
- Concrete Handling and Placing
- Plastic Concrete Finishing
- Shrinkage Cracks
- Curing
- Formwork Removal
9.7 TES TING LABORATORY
- Contractor provides its own testing Laboratory
- All equipment provided as listed in the contract
9.8
- Test results verified for accuracy during inspection and periodic
audit
CONCRETE BATCHI NG PLANT
- Periodic calibration
- Equipment Preventive Maintenance Program
- Mixer blade end gap from face of drum (max= 7 mm) checked daily
- Compliance to concrete uniformity (ASTM C-94)
9.10 CONCRETE PLACEMENT
The concrete is placed with help of the concrete pump
10.0 ENVIRONMENT IMPACT: At locations where pollution level has
already exceeded the permitted level or is on higher side, every
construction activity needs very close scrutiny to ensure that there is
no further environmental degradation. Planning for method of
construction and type of materials used plays a very vital part in
containing the adverse environmental impact.
10.1 ACTION TAKEN TO REDUCE NAGETIBVE ENVIRO NMENT
IMPACT
a) The pre-stressing technique, was used extensively on the elevated
track to bind the segments, reduces the weight and volume of structure
thus correspondingly reducing pollution in manufacturing,
transporting, and assembling, etc.
b) Use of high strength concrete to optimum level substantially
reduced not only transportation and erection cost but also mitigated
pollution. Similarly, by appropriate use of ‘pre-stressing’ in concrete
structure, economy is invariably achieved as there is reduction in
volume from 20% to 40% in most of the cases, which in turn results in
a positive impact on environmental during construction.
c) Some of the other environmentally friendly construction practices
employed during the construction of the metro included
1. Tyre washing facility at site exits,
2.
provision of oil separators,
3.
Recycle of bentonite and reuse /recycle of curing waste
productive.
4.
Use of dewatered water etc.
5.
Maintenance of equipment is mandatory and requirements
for use of silent DG sets is made more stringent.
6.
Segregation of wastes at sites was initiated and handling of
waste as per legal requirements was
introduced.
11.0 CONCLUSION
Apart from the advantages mentioned in the beginning of this report
there are a number of environmentally sustainable advantages of
DMRC
1. In operation, it is a non polluting and environmental friendly
system
2.
It has a very high carrying capacity to cater to huge
passenger demands thus drastically reducing land acquisition
for the same load
3.
It requires much less space to carry same number
of
passengers
4.
Energy requirement per passenger kilometer is one fifth than
for other modes
5.
Finally, it is fast, reliable, safe and comfortable, all at the same
time